put a movie texture on a plane, choose the shader GLSL_Keyer in the material inspector. Choose the more light and dark background with the color picker,by picking the colors somewhere on your screen... and adjust the differents cursors...

//Chromakeyer shader for Unity 3D, done by Eric Wenger ( http://www.metasynth.com/ERICWENGER/ ) in april 2014, Alpha version, shared by noomuseum.net feel free to use.// put a movie texture on a plane, choose the shader GLSL_Keyer in the material inspector. Choose the more light and dark background with the color picker,// by picking the colors somewhere on your screen... and adjust the differents cursors...